Now to a cautionary story as we head into the summer months. A 3-year-old boy slips under water in a swimming pool. The only person who noticed, another little boy nearby. Adrienne Bankert has more. Reporter: Tonight, that toddler, alive after the heroic acts of perfect strangers. Surveillance video, capturing the moment. The 3-year-old boy went under at pool in Tallahassee, Florida. His head, bobbing as he struggled. Others in the pool, unaware. Nearly three minutes passing by, until 9-year-old colbi noticed what was happening. I thought, "Wait a minute, he's underwater and I don't even think he could swim." Reporter: Colbi pulling the boy up, and alerting grownups who carried the child's motionless body out of the pool. Colbi's mom a registered nurse, sprang to action. I started to administer cpr all my focus was on come on baby come on baby. Reporter: The toddler revived, making a full recovery. Him and his mom saved my baby's life and I thank them so much. Reporter: Children aged one to four are most likely to drown after two minutes under water a child will lose consciousness four to six minutes under water can cause irreversible brain damage. Colbi saving a life and learning a life lesson. Take care of the people you don't know. You should just help them even though you don't know them. Reporter: First responders say his thinking made a vital difference. They're calling them both heroes. Still ahead, that time of year, shark season.

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